Electrical cables are used extensively in oil wells to power various pumps located many feet below the surface. These cables must be able to survive and perform satisfactorily under extremely adverse conditions of heat, mechanical stress and pressure. In particular, these cables experience down-hole pressures which can be in the hundreds or thousands of pounds per square inch. Typically, the insulation surrounding the conductors in the cable contains micropores into which gas is forced at these high pressures over a period of time. Then, when the cable is rather quickly extracted from the well, there is not sufficient time for the intrapore pressure to bleed off. As a result, the insulation on the cable tends to expand like a balloon and can rupture, rendering the cable useless thereafter.
While there has been much work in this area of protecting down-hole insulated electrical cables to avoid explosive decompression by adding reinforcing layers, there are numerous disadvantages to the prior art. Thus, many of the prior art devices are extremely expensive to manufacture, are bulky and include numerous extra layers of protective material.
Examples of such devices are disclosed in the following U.S. Pat. Nos. 2,544,233 to Kennedy; 2,690,984 to Crandall et al.; 3,462,544 to King; 3,602,636 to Evans; 3,649,744 to Coleman; 3,742,363 to Carle; 3,835,929 to Suman, Jr.; and 4,096,351 to Wargin et al.